In an engine used for an automobile or the like, an exhaust turbocharger is widely used, in which a turbine is rotated by exhaust gas energy of the engine and a centrifugal compressor directly coupled to the turbine via a rotation shaft compresses intake air and supplies the engine with the intake air, to improve the output of the engine.
Such an exhaust turbocharger is required to have a lifetime of hundreds of thousands kilometers for automobiles, equivalent to that of the automobiles, or a lifetime of more than a million kilometers for trucks and buses.
However, an operation history (e.g. operation time, rotation speed, and cumulative damage level) of a turbocharger is not sufficiently understood. Further, a turbocharger is required to have a high reliability, and thus to be designed with sufficient safety, which results in having a high spec in terms of material strength (high strength, high durability) and a high cost.
Meanwhile, with regard to the lifetime estimation of turbochargers, Patent Document 1 (JP2002-544443A, translation of a PCT application) discloses an invention related to a fatigue-lifetime monitoring device for a turbocharger.
The document discloses a sensor for measuring a rotation speed of a rotation shaft of a turbocharger, a unit to calculate an actual malfunctioning probability of a turbocharger by processing rotation-speed information from the sensor to compare the actual malfunctioning probability of the turbocharger with a preset malfunctioning probability of the turbocharger, and displaying excess to prompt maintenance if the actual probability is greater than the preset malfunctioning probability of the turbocharger as a result of the comparison.
Further, the document also discloses inputting an inlet temperature of a turbocharger turbine as information, and a central processing unit and a storage unit provided in a package independently from, or as a part of, an engine control module.